Not Applicable.
Not Applicable.
1. Field of the Invention
The invention relates to a sampling system. Preferably, the invention relates to a stream switching system for fluid analysis.
2. Description of the Related Art
It is often very important to know what fluids are flowing through a conduit such as a pipeline. For example, a buyer and seller of gas may agree upon a price for the fluid flowing through a process pipeline based upon the content of the fluid stream. Thus, the fluid content must be measured. Where multiple pipelines are positioned near one another, it may be economical to use a single meter or measurement device to monitor all of the fluid flows. The device used to extract and deliver the fluid to the measurement device is traditionally referred to as a sampling system. The sampling system provides fluid sample to a measurement device such as a gas chromatograph.
FIG. 6 shows a xe2x80x9cdouble block and double bleedxe2x80x9d stream switching system for selectively supplying various fluid samples to downstream devices such as sample valves. The stream switching system 600 includes four streams 601-604 upstream of a stream-handling portion 691. The four streams include a calibration sample 601, stream 1602 corresponding to a first fluid sample, stream 2603 corresponding to a second fluid sample, and stream 3604 corresponding to a third fluid sample.
Streams 601-604 supply various fluid samples and connect respectively to actuatable calibration port 611 and actuatable stream ports 612-614. Actuatable ports 615-616 and 632-633, as well as ports 631 and 634, are also part of the sample-handling portion 691. Each actuatable port may be actuated into either an open or closed state as controlled by eight connected solenoids 650-657 (also labeled SV1-SV8) which correspond respectively to ports 611-616, 632-633. When a port is in an open state, fluid may pass freely through the port. When a port is in a closed state, fluid is prevented from flowing through that port. Also shown in FIG. 6 are solenoid pressure line 658 and solenoid vent line 659, as well as gas path 642 extending from port 615 to ports 633 and 632.
Each actuatable stream port 612-614, as well as actuatable calibration port 611, is positioned in an area 620 that creates a common sample path. Also positioned in the common sample path 620 are an actuatable xe2x80x9cblockingxe2x80x9d port 615 and an actuatable xe2x80x9cbleedxe2x80x9d port 616. In addition, area 621 creates a first sample shut off that contains two xe2x80x9cblockingxe2x80x9d ports 632 and port 631. Area 622 creates a second sample shut off that contains two xe2x80x9cblockingxe2x80x9d ports 633 and port 634. As shown, ports 632 and 633 are actuatable, while ports 631 and 634 are not.
Two channels, channel 1640 and channel 2645, are output tubing that direct fluid sample away from the stream switching system. The channels connect to, for example, downstream gas chromatographs including valve, heating, and measurement devices. Each channel thus may be separately analyzed by a gas chromatograph. Each channel can also be used as a flow path to xe2x80x9cbleedxe2x80x9d the system when switching from sample point to sample point.
As can also be appreciated, first and second sample shut offs correspond to first and second channels 640, 645. Consequently each channel is associated with two solenoids 650 and 657, either one of which can be actuated to prevent the flow of any fluid through the channel. In the illustration, the flow of fluid through channel 1 may be prevented by closing either actuatable blocking port 615 or actuatable port 632 in the first sample shut off. Similarly, the flow of fluid through channel 2 may be prevented by closing either actuatable blocking port 615 or the actuatable port 633 in the second sample shut off. Thus, because the flow of fluid may be prevented through a channel at either of two locations, this is a xe2x80x9cdouble blockxe2x80x9d design. In addition, the system may be bled through sample bleed port 616. Thus, because the system may be bled either through a channel or through the sample bleed port 616 the embodiment is a xe2x80x9cdouble bleedxe2x80x9d design.
Referring now to FIG. 7, a side exploded view of the stream switching portion 691 is shown. The stream switching portion constitutes upper, middle, and lower plates aligned and connected together by dowel pins 770 and torque screws 771-775. The lower plate, referred to as a manifold plate 710, includes eight actuation ports 711-718 connected by tubing to solenoids 650-657 (not explicitly shown in FIG. 7). The middle plate, also called a piston plate 720, includes eight locations 721-728 designed to receive respective pistons 750-757. Middle plate 720 also includes shallow channels, chambers, or grooves that form areas 620-622, as described with reference to FIG. 6. The upper plate, referred to as the primary plate 730, includes screw holes corresponding to the torque screws, as well as three exemplary fluid ports 616, 632, and 631. Eight pistons 750-757 (corresponding to ports 611-616, 632-633) as well as a pair of actuating diaphragms 740 lie between manifold plate 710 and middle plate 720. Sealing diaphragm 765 and cushion diaphragm 760 lie between the primary plate 730 and middle plate 720. The sealing and actuating diaphragms may be made from KAPTON polyimide film.
Each solenoid is placed in a closed position by the application of actuation gas from connected tubing. The application of the actuation gas for each individual solenoid is, in turn, controlled by a processor and associated software.
Although this stream switching system has significant advantages over previous designs, the use of actuating diaphragms, plates, and numerous pistons makes the system more expensive than is desirable. In addition, in the unlikely event that the electrical power to the solenoids is turned off and the carrier gas stream fails, sample leaks through the system. Although such a circumstance is uncommon, any leakage of the sample is undesirable.
A stream sampling system is needed that is less expensive than those previously in existence. This stream sampling system should be more resistant to operational failure than previous stream sampling systems is needed. Ideally, such a novel system could be compatible with the processor and software used with previous systems to enable single substitution of the novel system for the old.
One embodiment of the invention features a housing with an exterior, and a common stream path with connected first port, second port, and third port. Flow switches connect to the three ports and to three fluid sources, each flow switch being actuatable between an open position that allows flow of fluid from said the corresponding fluid source through said flow switch and a closed position that prevents the flow of fluid from the fluid source. Advantageously, each switch is in a closed position in the absence of electrical power applied to the switch.
Tubing is attached to the housing and may connect the common stream path to additional stream shut off solenoids. The housing is preferably a one-piece housing made from stainless steel. It also preferably includes a heating channel for warming fluid sample to a desired temperature.
Thus, the, present invention comprises a combination of features and advantages that enable it to overcome various problems of prior devices. The various characteristics described above, as well as other features, will be readily apparent to those skilled in the art upon reading the following detailed description of the preferred embodiments of the invention, and by referring to the accompanying drawings.